How Grep Got its Name

How did grep get its name? This all starts back with ed, the original unix
editor. ed was a command-line editor that worked identically to the
colon-commands in vi and vim–in fact, you can press Q to get into ed mode
(then type vi to get back into vim). From the ed editor you can issue common
line-oriented commands like s, d, y, and so on:

:%s/rdoc/docr/g
:/include/d

If you’re following along at home you may wonder “how can I see the contents of
this file?” Well if you just want to see every line you can use %p (% is
“the whole file”, and p is “print to screen”), though it’s more likely that
you want to see a small series of lines. 10,20p will show you lines 10
through 20, but maybe it makes more sense to see all lines matching a regular
expression.

From ed, to see all lines matching “include”, use g/include/p. To see all
lines matching “docr” use g/docr/p. In general, to see all lines matching
the regular expression “re”, use g/re/p.